1. Field of the Invention
The present invention related to a tray pressing device in a retort sterilizer for cooking foods such as pouched foods or packaged foods.
2. Discussion of the Prior Art
The conventional pressing device for tray covers housed in a rotary type of the retort sterilizer wherein the pouched foods are sterilized and cooked under high-temperature and high-pressure is disclosed by Japanese Utility Model Publication No. Sho 53-50695. The pressing device which has a plurality of tray covers located on each line of stacked trays at the uppermost stage and is freely operated externally of the retort, at the same time is enable to be shutted as well as a constant differential pressure is always maintained with regard to the pressure in the retort so as to ensure the accurate closing thereof.
Nevertheless, this device requires a complicate mechanism comprising a rotary shaft, a connection shaft, and a pressurizing pump, because it employs a structure in which hot water is circulated in the retort as well as the rotation of a cage occurs simultaneously.
Japanese Patent Disclosure No. Sho 56-88785 discloses a method of loading a basket in a rotary type of retort sterilizer set up in horizontal situation and its apparatus. This technology also uses the rotary cage comprising a body frame and right and left rollers. It cannot avoid the complicate structure either due to the provision of the rotary cage.
The conventional device adopting not the rotary type but a stationary type either uses a void tray or is equipped with the tray cover at the uppermost stage so as to prevent the relief of the pouched foods. In the former case, however, when stacking up the void tray, a line of automatic stacking up and conveying devices must be incorporated so that the tray at the uppermost stage may be void, and on the other hand, the latter case needs the installation of the tray cover and its adjustment.